Transport of the essential nutrient iron into bacterial cells is accomplished by low molecular weight chelators called siderophores. Intracellular release of iron is thought to be accomplished by reduction from the ferric to the ferrous state, but little is known of the process. According to this proposal, kinetic studies of ferric siderophore reduction will be performed. Reductants will include iron-sulfur proteins and their synthetic analogs. Also included in this proposal is the preparation of a synthetic siderophore which will find great utility in investigations of the mechanism of ferric siderophore transport.